A group of histamine H.sub.1 -antagonists discovered by George S. Sach are disclosed in European patent application No. 107,914 as aminopyrimidinone derivatives which may be depicted as: ##STR2## wherein R.sup.1 is halogen, nitro, amino or alkyl; R.sup.2 is halogen, nitro, amino, alkyl or alkoxy, R.sup.4 is phenyl or substituted phenyl where the substituent may be halo, hydroxy, alkyl, alkoxy or methylenedioxy and n is 3-5.
Schiehser et al., U.S. Pat. No. 4,490,527, discloses a series of histamine H.sub.2 -antagonists which are thieno- or benzo-isothiazole amines N-substituted by an aryloxyalkyl group or moieties common to ranitidine and tiotidine.